I've been trying to solve the following problem for three weeks on my own and have made no progress, and have probably made things worse. So, I figured it was time to get some help at long last.
I bought my S4 I9500 in Bangkok, and I was not aware that Samsung was region locking their phones now, as I had an S2 that I used in Thailand, China and Cambodia without any problems.
So, I bought the S4 and loved it. However, I moved back to China last month, and upon arrival I bought a SIM card. It didn't work... At this point, my firmware was 4.3, as it had auto-updated from 4.2 while I was in Thailand.
The folks at China mobile couldn't figure out the problem, so I did some research and found out that my phone was region locked. I went to 3 Samsung stores here, and none of them knew what to do, nor would bother to figure it out.
So, I had to try to fix it on my own. I read about entering service mode and tried it, but it didn't work. From what I read, it would have worked in 4.2.2, but not 4.3. I tried finding a place to download 4.2.2 to flash it back, but Hotfile is dead, so I got 4.4. I figured it couldn't hurt, right?
Well, it didn't help.
So, basically, my I9500 is at firmware version 4.4, and my phone is still locked. I am in desperate need of some help. I do not care about the warranty, as I am pretty sure I screwed that up already.
BTW: I did try some sites for the unlock codes, but either they didn't have what I needed, the IMEI code was not accepted, only accepted Paypal, or would not accept a UnionPay credit card. -_-
Thanks for your time.